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Posterior auscultation of mechanically ventilated patient is challenging. Environmental ICU noises make the detection of subtle auscultatory features difficult. Digitalized pulmonary acoustic monitoring has recently been introduced in the ICU. We explored the possibility to listen to sound waves recorded by the VRI system.
Lung sounds were recorded for 20 seconds using two arrays of 17 piezoelectric contact sensors attached to the patient's back in a supine position. Sound files were archived in a WAV format for offline analysis. Three physicians and one trained respiratory therapist, blinded to the patient's clinical status, provided their findings while listening to sound waves recorded by 12 sensors distributed from apex to base, six from each lung. Breath sounds were categorized as normal versus abnormal and adventitious lung sounds were characterized as wheezes, rhonchi or crackles. Findings were compared with anterior stethoscope auscultation performed at the time of the recording by one of the physicians.
Eighteen critically ill mechanically ventilated patients (age 65 ± 17) were enrolled in this study. Chest radiography (CXR) findings included consolidation in 13 patients. There was an agreement among at least three clinicians in the normal/abnormal classification. Furthermore, in 10 out of these 15 patients (67%), this assessment based on sound wave analysis was in agreement with anterior stethoscope auscultation. Finally, the physician who performed both sound wave analysis and stethoscope auscultation reported crackles/rhonchi in five out of 13 patients with consolidation (38%) during sound wave analysis but only in one patient during auscultation (8%).
The level of interobserver variability for sound wave characterization was comparable with levels usually reported during stethoscope auscultation. However, in patients with consolidation, a higher number of crackles/rhonchi was reported during posterior sound wave analysis than during anterior stethoscope auscultation. This discrepancy may be either due to the anterior/posterior orientation or to the higher sensitivity of the offline sound wave analysis.